With the recent development of technologies allowing liquid crystal display devices or organic EL display devices to have a large area, high luminance and high resolution, demands for high performance materials supporting the devices are growing. Accordingly, device structures of liquid crystal display devices or organic EL display devices have become more complicated. Consequently, high resolution materials capable of forming micropatterns are preferable as an insulating layer used for forming a via hole in an ultrathin film transistor (TFT) for driving signals, and as a bank material for forming pixels of an organic EL display device.
In a manufacturing process of the above-mentioned display devices, a pattern forming process producing the above-mentioned constituents is generally carried out through a photolithography process. In order to form micropatterns through such a photolithography process, a resist composition is generally used.
Such a resist composition may process a via hole or form a bank pattern through a photolithography process, and in order to obtain patterns with high resolution, the composition needs to be readily developed in a thin alkali developing liquid, and needs to form an intermolecular crosslinked bond through a curing process to have chemical resistance, heat resistance and post-process reliability.
Existing positive resists for an insulating layer have normally used materials combining acryl-based binders and naphthoquinonediazide compounds (Japanese Patent Application Laid-Open Publication No. H10-153854) and the like, however, heat resistance thereof is significantly insufficient to withstand a high temperature ITO heat treatment process, and these materials are used only in processes using amorphous ITO.
These materials are not able to be used in low-temperature poly silicone (LTPS) processes that have recently received attention as a back plane for organic EL display devices due to insufficient heat resistance. Meanwhile, materials combining polyimide-based binders and naphthoquinonediazide compounds (PCT/JP2002/01517) have high post-process reliability, and are suitable as a bank forming material for forming pixels of an organic EL display device, but have problems of excessively high raw material costs and a panel price increase caused therefrom, and losing half the solubility declining effect of quinonediazide due to excessively high alkali solubility of a polyamic acid precursor.
In addition, precursor compounds in which a carboxylic acid group is protected by an ester group for compensating high solubility of a polyamic acid precursor have problems in terms of a process in that synthesis steps increase, yields decrease and excessively high exposure is required. Moreover, polyimide-based resins have an aromatic ring as a basic skeleton and the resin itself has dark yellowish brown color, and therefore, the polyimide-based resins have low light transmittance in a visible region, and controlling a pattern residue problem or controlling a development property is not simple due to the excessively rigid skeletal structure.
Accordingly, demands for the development of new positive resist compositions in which heat resistance, a development property for a thin alkali solution, high resolution and high sensitivity properties are all excellent have been ongoing.